Bioleaching black shale in Western Australia

Octava Minerals Limited (ASX:OCT) is an exploration company whose most distinctive idea is bioleaching: using microbes to pull rare earths, lithium and vanadium out of black shale at its Byro project in the Gascoyne region of Western Australia. It also holds the Federation polymetallic project in Tasmania and a farm-in joint venture with Future Metals NL (ASX:FME) in the East Kimberley. All of it is exploration-stage.

The Byro exploration target

In its Quarterly Report of 31 July 2026, the company disclosed an exploration target of 4.9 to 7.4 billion tonnes of mineralised black shale at Byro. Grade ranges are 207 to 431 parts per million (ppm) total rare earth oxides, 159 to 331ppm lithium oxide and 173 to 359ppm vanadium oxide, over an area of about 12 by 14 kilometres within 50 metres of surface.

An exploration target is a conceptual range, not a JORC Mineral Resource. The figures may change or never be realised, and the grades are low in absolute terms, so processing cost matters.

That is where bioleaching comes in. The quarterly report says tests by CSIRO and BiotaTec recovered 70 to 80 per cent of critical minerals from Byro shale over 21 days. Those are laboratory results. Cost and scalability have not been demonstrated. During the June quarter the company also completed the Acquisition of 100 per cent of Byro, which comprises two granted exploration licences covering 555 square kilometres.

Tasmania and the Kimberley

At Federation, Octava drilled eight diamond holes, which the company describes as the first drilling there in more than 50 years. Reported intercepts include 6 metres at 0.79 per cent copper, 0.59 per cent tin, 336.7ppm indium and 93.9ppm silver from 130 metres in hole OFD005, and 2 metres at 1.85 per cent antimony, 2.38 per cent lead and 7.95 per cent zinc in OFD003. The company says the sulphide target remains open at depth. These are single-hole intercepts, not a resource.

Cash and funding

The latest Appendix 5B retrieved in full for this article is for the March 2026 quarter, lodged on 29 April 2026. It showed cash of $1.035 million with no debt, net operating cash outflow of $196,000 and exploration spending of $508,000. The company calculated 1.47 quarters of funding and said it would slow exploration spending to match available funds. No Equity was raised in that quarter, although $1.5 million was raised in the nine months to 31 March 2026.

The June quarter balance was not retrieved, so the current position may differ. A short runway suggests further Capital raising at some point, which would dilute holders; that is typical for explorers and not distress on its own.

Risks and context

Unconventional deposits like black shale face a high bar. Octava must show that low grades can be processed economically at scale, convert a conceptual target into a resource, and fund that work with limited cash. Federation's results are early, and metal prices can shift the picture quickly.

Upcoming milestones

No confirmed dates have been announced. The next quarterly report is expected around 28 October 2026 and the Annual Report around 30 October 2026, though neither date has been confirmed by the company.